Show device message about removal of unencrypted messages

In its stead, remove `recode_avatar` high-level migration. It was added
5 years ago, and even if someone updates Delta Chat after such a long
time, large avatars are not a problem anymore since we don't send them
in unencrypted messages.

src/sql.rs

@@ -8,8 +8,7 @@ use anyhow::{Context as _, Result, bail};
 use rusqlite::{Connection, OpenFlags, Row, config::DbConfig, types::ValueRef};
 use tokio::sync::RwLock;
 
-use crate::blob::BlobObject;
-use crate::chat::ChatId;
+use crate::chat::{ChatId, add_device_msg};
 use crate::config::Config;
 use crate::context::Context;
 use crate::debug_logging::set_debug_logging_xdc;
@@ -214,32 +213,23 @@ impl Sql {
         // this should be done before updates that use high-level objects that
         // rely themselves on the low-level structure.
 
-        let recode_avatar = migrations::run(context, self)
+        let show_unencrypted_device_msg = migrations::run(context, self)
             .await
             .context("failed to run migrations")?;
 
         // (2) updates that require high-level objects
         // the structure is complete now and all objects are usable
 
-        if recode_avatar && let Some(avatar) = context.get_config(Config::Selfavatar).await? {
-            let mut blob = BlobObject::from_path(context, Path::new(&avatar))?;
-            match blob.recode_to_avatar_size(context).await {
-                Ok(()) => {
-                    if let Some(path) = blob.to_abs_path().to_str() {
-                        context
-                            .set_config_internal(Config::Selfavatar, Some(path))
-                            .await?;
-                    } else {
-                        warn!(context, "Setting selfavatar failed: non-UTF-8 filename");
-                    }
-                }
-                Err(e) => {
-                    warn!(context, "Migrations can't recode avatar, removing. {:#}", e);
-                    context
-                        .set_config_internal(Config::Selfavatar, None)
-                        .await?
-                }
-            }
+        if show_unencrypted_device_msg {
+            let txt = r#"To keep Delta Chat simpler and more secure, it no longer sends or receives messages that aren't end-to-end encrypted.
+
+Nothing is lost: your encrypted chats work as before, and old unencrypted chats remain readable.
+
+To keep sending and receiving unencrypted email, use a regular email app. You can find your email password in Delta Chat under "Settings → Advanced → Relays": tap (or right-click) your address and choose "Edit Relay".
+
+More details: https://..."#;
+            let mut msg = crate::message::Message::new_text(txt.to_string());
+            add_device_msg(context, Some("unencrypted-device-msg"), Some(&mut msg)).await?;
         }
 
         Ok(())
@@ -685,7 +675,18 @@ impl Sql {
 }
 
 pub(crate) trait TransactionExt {
+    /// Used for executing `SELECT COUNT` statements only. Returns the resulting count.
     fn count(&self, query: &str, params: impl rusqlite::Params + Send) -> Result<usize>;
+
+    /// Executes a query which is expected to return one row and one
+    /// column. If the query does not return any rows, returns `Ok(None)`.
+    fn query_get_value<T>(
+        &self,
+        query: &str,
+        params: impl rusqlite::Params + Send,
+    ) -> Result<Option<T>>
+    where
+        T: rusqlite::types::FromSql + Send + 'static;
 }
 
 impl TransactionExt for rusqlite::Transaction<'_> {
@@ -693,6 +694,21 @@ impl TransactionExt for rusqlite::Transaction<'_> {
         let count: isize = self.query_row(query, params, |row| row.get(0))?;
         Ok(usize::try_from(count)?)
     }
+
+    fn query_get_value<T>(
+        &self,
+        query: &str,
+        params: impl rusqlite::Params + Send,
+    ) -> Result<Option<T>>
+    where
+        T: rusqlite::types::FromSql + Send + 'static,
+    {
+        match self.query_row(query, params, |row| row.get::<_, T>(0)) {
+            Ok(res) => Ok(Some(res)),
+            Err(rusqlite::Error::QueryReturnedNoRows) => Ok(None),
+            Err(err) => Err(err.into()),
+        }
+    }
 }
 
 /// Creates a new SQLite connection.

src/sql/migrations.rs

@@ -717,7 +717,9 @@ pub(crate) async fn msgs_to_key_contacts(context: &Context) -> Result<()> {
 fn unencrypted_chats_migration(
     context: &Context,
     transaction: &mut rusqlite::Transaction<'_>,
-) -> Result<()> {
+) -> Result<bool> {
+    let mut show_unencrypted_device_msg = false;
+
     // Migrate:
     // - all unencrypted (i.e. ad-hoc) groups into regular groups with 0 members.
     // - all unencrypted 1:1 chats into a group with 0 members. (probably unnecessary, not implemented right now)
@@ -764,7 +766,6 @@ WHERE fingerprint='' AND id>9 AND name='' AND authname=''
 ",
     )?;
 
-    // Set the gray letter avatar for all legacy chats:
     let legacy_chats =
         transaction.count("SELECT COUNT(*) FROM temp.legacy_unencrypted_chats", ())?;
     let legacy_contacts = transaction.count(
@@ -772,6 +773,7 @@ WHERE fingerprint='' AND id>9 AND name='' AND authname=''
         (),
     )?;
     if legacy_chats > 0 || legacy_contacts > 0 {
+        // Set the gray letter avatar for all legacy chats:
         let blob = crate::blob::BlobObject::create_and_deduplicate_from_bytes(
             context,
             include_bytes!("../../assets/icon-unencrypted.png"),
@@ -782,16 +784,23 @@ WHERE fingerprint='' AND id>9 AND name='' AND authname=''
             "UPDATE chats SET param=? WHERE id IN (SELECT chat_id FROM temp.legacy_unencrypted_chats)",
             (new_param,),
         )?;
-
         transaction.execute(
             "UPDATE contacts SET param=? WHERE fingerprint='' AND id>9",
             (new_param,),
         )?;
+
+        let force_encryption: Option<String> = transaction.query_get_value(
+            "SELECT value FROM config WHERE keyname='force_encryption'",
+            (),
+        )?;
+        if force_encryption == Some("1".to_string()) {
+            show_unencrypted_device_msg = true;
+        }
     }
 
     transaction.execute("DROP TABLE temp.legacy_unencrypted_chats", ())?;
 
-    Ok(())
+    Ok(show_unencrypted_device_msg)
 }
 
 impl Sql {
@@ -893,7 +902,7 @@ pub async fn run(context: &Context, sql: &Sql) -> Result<bool> {
     }
 
     let dbversion = dbversion_before_update;
-    let mut recode_avatar = false;
+    let mut show_unencrypted_device_msg = false;
 
     if dbversion < 1 {
         sql.execute_migration(
@@ -1268,7 +1277,7 @@ CREATE TABLE imap_sync (folder TEXT PRIMARY KEY, uidvalidity INTEGER DEFAULT 0,
             .await?;
     }
     if dbversion < 77 {
-        recode_avatar = true;
+        // removed
         sql.set_db_version(77).await?;
     }
     if dbversion < 78 {
@@ -2772,7 +2781,7 @@ CREATE TABLE smtp_success (
     if dbversion < migration_version {
         sql.execute_migration_transaction(
             |transaction| {
-                unencrypted_chats_migration(context, transaction)?;
+                show_unencrypted_device_msg = unencrypted_chats_migration(context, transaction)?;
 
                 Ok(())
             },
@@ -2795,7 +2804,7 @@ CREATE TABLE smtp_success (
     }
     info!(context, "Database version: v{new_version}.");
 
-    Ok(recode_avatar)
+    Ok(show_unencrypted_device_msg)
 }
 
 #[cfg(test)]